Company boss recruits two learners to make instrument (5)
I believe the answer is:
cello
'instrument' is the definition.
(cello is a kind of instrument)
'company boss recruits two learners' is the wordplay.
'two learners' means two replacements for 'learner'.
'company boss' becomes 'CEO' (chief executive officer).
'recruits' indicates putting letters inside.
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'learner' becomes 'l' (as in a learner driver with L-plates on their car).
'l'+'l'='ll'
'ceo' going around 'll' is 'CELLO'.
'to make' is the link.
(Other definitions for cello that I've seen before include "10 [INSTRUMENT]" , "Orchestral instrument played between the legs" , "Musical instrument like large violin held between knees" , "Large stringed instrument" , "music produced by this?" .)